Probing Question: Are 'superfoods' really nutritional powerhouses?

Acai berries
Flickr Creative Commons, Breno Peck

Acai berries

You've probably seen the supermarket tabloid articles with titles like "The 12 Foods Everyone Should Eat!" or "Four Foods for Peak Performance!" Every week there's another berry, grain, or bafflingly-named compound that's the key to better health, longer life, and peace in our time. But do these "superfoods," as they are called, deserve the hype? Or is the moniker just a marketing tool to sell us food and supplements we don't really need?

It's a little of both, says Penny Kris-Etherton, distinguished professor of nutrition in the Department of Nutritional Sciences at Penn State. "Nutritionists don't have a definition for ësuperfood,' " she notes. What might well deserve the label "super," though, is "a food that has a high nutrient density, or contains bioactive components with proven health benefits."

In our era of "supersized" snack foods with lots of calories and scant nutritional value, Kris-Etherton says, nutrient density is vital. "Research is beginning to show that restricting calories can have health benefits beyond weight loss, such as extending life span." However, "There are a lot of ways to practice caloric restriction. One way is just to cut calories, regardless of whether you're cutting nutrients. This isn't good because you won't meet nutrient recommendations for good health. A better way is to cut calories but not nutrients, and to do that, you really need nutrient dense foods."

A bioactive component, on the other hand, is a compound that has known health benefits but that, unlike essential nutrients—the vitamins and minerals our bodies need daily—is not required to achieve a nutritionally adequate diet. "The key one I can think of," says Kris-Etherton, "is resveratrol, which seems to be an anti-aging compound." Resveratrol is found in grape skins, among other sources, though how much is necessary to obtain a benefit is still under debate. Current research suggests that it is a lot—much more than we can get in a typical healthy diet.

Some of the foods making headlines, such as aça'berries, pomegranate juice, green tea, and goji berries, boast high antioxidant content, she notes. Others, such as yogurt and kefir, are thought to promote good digestive health, and still other foods—such as seaweeds and green leafy vegetables—are known for their mineral content and phytochemicals like beta-carotene.

The problem with superfoods, says Kris-Etherton, is that people may overestimate their power. "There is no one food that provides everything your body needs," she says, "We have be careful using that term.' They're not magic foods. We must pay attention to the total diet."

"But," she concedes, "the so-called superfoods do have some health benefits, especially when they're incorporated into a healthy diet." Consuming a variety of foods, including lots of fruits and vegetables, along with other plant foods such as whole grains, legumes, and nuts and seeds, gives a person the best chance of obtaining the full spectrum of nutrients and bioactives, she says.

Preparation is important, too. "Cooking some vegetables makes the nutrients more available," says Kris-Etherton. "With cooked carrots, for example, you get more of the carotinoids, but on the other hand, if you cook veggies too much you can destroy heat-sensitive nutrients like vitamin C. So you have to balance this with a variety of food preparation techniques."

Many other factors affect the absorption of nutrients. Some vitamins, for instance, are fat soluble, and in order to get their full benefit, a person's diet must include fat. In a recent study, she notes, a tomato-based salsa eaten with fat-laden avocado was shown to be better for vitamin A uptake than salsa alone.

In the end, Kris-Etherton tells us what we should already know: the best way to ensure a long, healthy life is to eat a balanced diet that contains a variety of foods and plenty of fruits and vegetables. "What I think people should do with all this new information is stay tuned. We've got to get to where there is a large evidence base before nutritionists will say, ëI think you should take this for these reasons.' "

But there are some foods, besides the ubiquitous fruits and vegetables, that everyone should be eating. "Fish!" Kris-Etherton says. "I recommend that people consume two servings of fish per week. We're also seeing more and more about the health benefits of consuming wine and alcohol in moderation, so that's another one to think about. And then there's a lot of research on dark chocolate, in terms of cardiovascular benefits and insulin sensitivity. That's just the tip of the iceberg."

So, then. Salmon for dinner, a glass of wine, and chocolate for dessert: three superfoods almost everyone can get behind. And, don't forget to include generous portions of fruits and vegetables, as well!

Penny Kris-Etherton, Ph.D., R.D., is Distinguished Professor of Nutrition in the Department of Nutritional Sciences in the College of Health and Human Development. You can reach her at pmk3@psu.edu.

Last Updated August 11, 2009